In recent years, the oil and gas exploration and production industry has made increasing use of expandable tubing for use as bore-lining casing and liner, in straddles, and as a support for expandable sand screens. Various forms of expansion tools have been utilised, earlier proposals including expansion dies, cones and mandrels which are pushed or pulled through tubing by mechanical or hydraulic forces. More recently, rotary expansion tools have been employed, these tools featuring rolling elements for rolling contact with the tubing to be expanded while the tool is rotated and advanced through the tubing.
Each of the these expansion apparatus offers different advantages, however there is a limit to the degree of expansion that is achievable using such expansion tools.
It is among the objectives of embodiments of the present invention to provide a method of expanding tubing downhole which permits a relatively large degree of expansion to be achieved.